A fine pattern that is used in a display device such as a semiconductor circuit device, LCD, and PDP is formed by photolithography using a photoresist. The photolithography has an advantage in that a desired pattern may be precisely obtained, but is disadvantageous in that many processes should be performed, many types of materials are used to maximize a photoresist effect, and a great amount of photoresist is used during processes such as coating.
Accordingly, currently, as a next generation process to overcome the disadvantages of the photolithography, a technology for obtaining a fine pattern by using a roll printing or inkjet printing method is suggested.
In the formation of the fine pattern by using the roll printing, various types of methods such as offset printing, reverse offset printing, roll-to-roll printing and the like may be used, and they may be extensively applied to colors of R (Red), G (Green), and B (Blue) that are constituent elements of a color filter, a BM (Black Matrix) pattern, a pattern for forming electrodes of thin film transistors (TFT) and plasma display panels (PDP), and pattern transferring of a partition material.
In the case of the reverse offset printing that is one of the representative roll printing process, a pattern is formed by three steps of coating ink from a coater to a blanket, transferring an undesired pattern from a blanket by a cliche, and transferring the pattern that remains on the blanket onto a glass substrate, and a roll printing device may generally include a coater, a roll, a roll driving device, a cliche or a substrate stage, and a driving device for aligning the stage as the most basic constituent element, a cliche and/or pipe washing device, a drying device for drying the blanket by absorbing a solvent absorbed on the blanket, and various types of sensor devices.
The degree of precision and a pattern transferring effect of a pattern that is formed by using the roll printing method largely depend on process conditions such as a coating state from a coater to a roll or a blanket of the roll, the degree of volatilization and a waiting time of a solvent before transferring onto the cliche or the substrate after the coating, and an impression pressure that is formed by an interval between the stage and the roll or the blanket during the transferring.
In particular, the uniformity of the entire pattern and formation of various types of stains are determined by a coating state during the coating onto the roll or the blanket that is a first step of the roll printing process. However, in general, since the blanket that is used in the roll printing is made of PDMS (polydimethylsiloxane) having the very low surface tension, in order to form the good coat film by coating ink thereonto, it is required that the surface tension of the ink is lower than that of PDMS.
Since PDMS generally has the surface tension of 24 mN/m or less, in order to desirably coat the ink onto PDMS of the blanket in roll printing, it is required that the surface tension of the ink is lower than 24 mN/m. However, since there is a limit in reduction of the surface tension by using a hydrocarbon surfactant or a silicon surfactant in order to set the surface tension of the ink to 24 mN/m or less, it is most preferable that the fluorine surfactant is used.
In general, in views of structure, the fluorine surfactant includes a fluorine component that has all hydrophobicity and lipophobicity and most largely affects the reduction of the surface tension and a hydrophilic component and a lipophilic component to improve compatibility to used solvents, various types of resins, pigments, and additives.
Therefore, the fluorine surfactant may be roughly classified into three categories: a surfactant that includes a fluorine component and a hydrophilic component, a surfactant that includes a fluorine component and a lipophilic component, and a surfactant that includes a fluorine component, a hydrophilic component, and a lipophilic component in views of constituent components according to a used system or a desired property. In addition, there is a fluorine surfactant that includes an ionic component.
Among them, as a fluorine surfactant that is capable of being used in electronic materials like ink for roll printing and largely affects reduction of the surface tension, the surfactant that includes the fluorine component and the lipophilic component, or the surfactant that includes the fluorine component and the hydrophilic component is most preferable.
However, in the case of them, in the structure of the surfactant, since there are the hydrophilic component or the lipophilic component in addition to the fluorine component having the hydrophobicity and the lipophobicity, the compatibility to other components that constitute the ink, for example, the pigment or the binder resin is reduced. Thus, there are problems in that a phase separation occurs, defoaming property is largely reduced, or holes are formed on a coating surface.
Therefore, among the fluorine surfactants, if a surfactant that includes the fluorine component and the lipophilic component and largely affects reduction of the surface tension or a surfactant that includes the fluorine component and the hydrophilic component is used in conjunction with a surfactant that includes the fluorine component, the hydrophilic component and the lipophilic component, the compatibility between pigments and binder resins constituting the ink and the fluorine surfactant is increased to largely reduce the surface tension. Accordingly, a coating property is improved in PDMS, defoaming property is improved, and problems such as the formation of holes on the surface may be solved.
In the ink for roll printing, in order to largely reduce the surface tension, in the case of when the fluorine surfactant that includes only the fluorine component and the hydrophilic component or the fluorine component and the lipophilic component and largely affects reduction of the surface tension is added, the coating property is excellent, but there is a problem in that the compatibility to other materials included in ink is reduced. Therefore, since defoaming property is reduced, fine bubbles that are not easily removed are formed, and holes having the puddle shape are formed on the coating surface of ink due to the fine bubbles.
Therefore, in order to solve this, if a surfactant other than the fluorine surfactant that includes only the fluorine component and the hydrophilic component or the fluorine component and the lipophilic component, that is, a hydrocarbon surfactant or a silicon surfactant, or a surfactant that includes all the fluorine component, the hydrophilic component and the lipophilic component among the fluorine surfactants is used, the compatibility is increased, thus improving defoaming property and suppressing the formation of holes on the coating surface. However, since the coating property is poor, there is a problem in that the ink is not desirably coated on the blanket during the roll printing.